The bearing that was used is the same one in a 4" electric forklift wheel, bearing #6204 2rs. The issue we had yrs ago with the manufactures was the lack of grease in the bearings. It wasn't every bearing, just a few out of a group of 100. They would fail within a week of install. Once we decided to repack the bearing with high temp red grease all problems stopped.
Just a side note S6204 2rs is the ceramic bearing, 5204 2rs is the double row bearing and I still haven't found the double row ceramic yet. But I don't think the double row was or is a good idea (personal opinion) because the they are actually weaker do to the fact that they can't load as many bearings in it. bearings can be found here
Ball Bearings:Miniature bearings:Ceramic Bearings:Bearing
I'm doing my clutch next month and have an idea I can do this bearing project for less than $150 out the door. I will be using this bearing 6204 2nse and leaving the seals on after repacking it with the high temp grease.